Question
A boy weighing 50kg is running with velocity 24km/hr jumps onto a cart of mass 100kg moving with velocity 12km/hr in opposite direction. What is the velocity of boy–cart system after the boy lands over the cart?
Solution
Given,
Mass of the boy, m1 = 50 kg
Mass of the cart, m2 = 100 kg
Velocity of boy,
Velocity of cart, 
Let V be the velocity of boy - cart system.
Using law of conservation of linear momentum,
50 x 24 - 100 x 12 = (50 + 100) x V
V = 0
Therefore, the velocity of the boy-cart system becomes zero after the boy lands on the cart.
